This invention relates to containers and is more particularly concerned with improvements in product containers which are in the form of a tray and which are adapted to be fabricated from paperboard or similar foldable sheet material of a character which will enable the container to be used for baking bread, or the like, and marketing the product in the tray in which it has been baked.
Tray containers have been developed heretofore which are particularly adapted for use in the bakery industry where the product may be processed in an oven and subsequently marketed without removing it from the container in which it has been processed. Products such as cakes, pastry, and the like are generally in a flowable state initially, that is, in a liquid or semi-liquid condition, and it is a requirement that the container be leakproof when filled to a predetermined level with the product and capable of withstanding oven temperatures during the baking process without damage from the heat so that the baked product may be marketed without removal from the container. For such products, containers have been developed which are adapted to be formed from thin metal foil or relatively stiff metallic sheet material which can be pressed or shaped to the desired form and become part of the final package in which the product is marketed. Such containers are generally expensive and lacking in esthetic appear since they do not readily accept the inks commonly employed in decorative printing. Efforts have been made, with some degree of success, to provide non-metallic trays which are suitable for this purpose. One such tray structure is disclosed in U.S. Pat. No. 4,114,797 granted Sept. 19, 1978. Trays of this type, which are formed from paperboard having a film-like heat resistant coating, have not been entirely satisfactory for handling some bakery products, such as bread, where a rectangular shape is desired so that the finished product will have the conventional rectangular shape of a loaf of bread. The plastic film employed for trays of this type generally has shrink characteristics which differ from paperboard with the result that the sidewalls buckle and have an unattractive appearance.
Consequently, there appears to be a need for trays of this type which have greater rigidity or stiffness, particularly in the sidewall panels so as to more nearly retain their shape during processing and which may be employed for processing in a microwave oven as well as in a conventional convection oven.
It is a general object, therefore, of the present invention to provide an improved open top tray structure of the type described which has greater rigidity in the sidewalls, which is more versatile in use, and more economical so as to compete with trays formed of metal foil, and the like.
It is a more specific object of the invention to provide an improved tray structure and a method of forming the same in which the tray is fabricated from a paperboard blank coated with a film forming heat resistant plastic material which is cut and scored, so that it can be set-up with sidewall panels upstanding from a rectangular bottom wall panel and connected at the corners by pairs of integral web members which are folded upon each other and against the outside faces of oppositely disposed sidewalls having narrow top flanges for reinforcing the sidewalls and with provision for anchoring the folded web members in position and having overlapping tab members forming corner connections between the top edge flanges.
It is a further object of the invention to provide a tray structure of the type described and a method of fabricating the same so as to provide integrally hinged top flange forming strip members on the sidewalls, with cut scoring at the hinge connection between the sidewalls and the top flanges which will prevent the difference in the contraction and expansion characteristics of the plastic film and the paperboard from buckling the sidewalls during processing of the tray and product in a baking oven.
The herein disclosed and claimed invention comprises a tray structure and a method of forming the same from a cut and scored blank of foldable paperboard which is coated with a heat resistant plastic film, which tray comprises a bottom wall forming panel and oppositely disposed pairs of peripheral sidewall forming panels which are integrally hinged to and disposed in upstanding relation with the bottom wall forming panel, with pairs of integrally hinged triangular web members at the intersecting corners, which web members are folded into overlying relation on the outside face of oppositely disposed sidewall panels and secured in position by means of a top edge flange formation adhesively adhered beneath an edge reinforcing strip in the form of a flange which is integrally hinged to the top edge of the associated sidewall forming panel on a hinge line defined by cut-scores in which the plastic film is severed by closely spaced small length cuts.